1. Field of the Invention
The present invention relates to a carbon-based material, for example, a nanometal-flake graphite composite including nanometal-flake graphite, in which crystallized nanometal particles are highly densely bonded to the surface of flake graphite, and a polydopamine coating layer, and more particularly, to a nanometal-flake graphite composite, in which properties, such as bonding properties between flake graphite basal planes, adhesiveness with other media, and dispersibility, are significantly improved by bonding polydopamine to the nanometal-flake graphite, and a method of manufacturing the nanometal-flake graphite composite.
2. Description of the Related Art
Recently, “polydopamine” mimicking adhesive proteins of mussels has received attention in various technical fields. Since the polydopamine is a mussel-inspired material, the polydopamine has excellent biocompatibility and may be coated on virtually all surfaces. Also, since the coating surface has activity, a new material may be introduced on the polydopamine coating. In a case in which polydopamine is introduced into various synthetic polymers/natural polymers, since these polymers also have adhesive and coating capabilities, these polymers are applied to various techniques.
Specifically, a study has been reported in which cell culture becomes possible on surfaces, such as those of polyethylene, silicon rubber, and polydimethylsiloxane (PDMS), on which cell adhesion is not possible, by introducing a polydopamine coating (S. H. Ku et al, Biomaterials 2010, 31, 2535), and an adhesive chitosan hydrogel is formed by introducing polydopamine into chitosan, as a natural polymer, which has been actively studied as a medical polymer and a hemostatic agent has been developed using the adhesive chitosan hydrogel (J. H. Ryu et al., Biomacromolecules 2011, 12, 2653). In addition, an adhesive polymer has been developed by introducing polydopamine into hyaluronic acid or polyethylene glycol (PEG), and thus, polydopamine has been variously used in medical/biotechnology industries, for example, biocompatible surface modification and hydrogel formation.
Applied research in the energy sector using polydopamine has recently received attention, wherein a study has also been reported in which adhesiveness is provided by introducing polydopamine into a polymer, such as alginic acid and polyacrylate, which is used as a binder of a lithium ion battery, to improve adhesion between the binder and an electrode, and thus, capacity and lifetime of the battery are significantly improved.
However, even with respect to the polydopamine having such excellent coating properties, bonding to pure flake graphite is not easy. The pure flake graphite has a very stable chemical structure itself due to the Van der Waals force between the flake graphite layers, and a bonding site is not present on a basal plane of the flake graphite but is present only at an edge or a defective part of the flake graphite. Thus, when coating of polydopamine is generally attempted on the pure flake graphite, only a portion of the edge and the defective part of the flake graphite is usually coated. Research into surface modification of the flake graphite or control of coating conditions has continued to address this issue.
The present inventors confirmed that, different from conventional flake graphite, coating properties of nanometal-flake graphite having a structure, in which nanoparticles are crystallized at a high density, with respect to polydopamine are excellent, thereby leading to the completion of the present invention.